Fatigue Loading of Reinforced Concrete Members Strengthened Using Carbon Fiber Reinforced Polymer Composites

The present thesis reports testing involving the static and fatigue performance of rectangular reinforced concrete (R/C) beams strengthened using epoxy bonded Carbon Fiber Reinforced Polymer (CFRP) composite materials. The overall objective was to establish the influence of fatigue loading on flexural behavior of strengthened R/C members.

Six specimens, strengthened using different configurations of CFRP flexible sheets and pultruded plates, were subjected to fatigue loading under various stress ranges representative of service-load conditions and potential overloading. Monotonic static tests to failure were conducted on five of these specimens after they had undergone a repeated loading sequence to a maximum number of 1,000,000 cycles.

Beams were extensively instrumented to monitor load, deflections, strains, and acoustic emissions over the entire spectrum of loading to failure. The post-cyclic static response is reported. Structural ductility and energy ductility indices are computed to describe the overall structural behavior.

Test results showed no evidence of damage propagation at the concrete-composite interface when beams were subjected to service-load cycling. Monotonic tests demonstrated no influence of the fatigue loading on the ultimate static capacity. However, post-cyclic ultimate deformations and structural ductility were reduced after cyclic loading. Fatigue performance under high stress range appeared to be governed by debonding at the concrete-adhesive interface. One specimen failed under fatigue loading. Test results are also compared with previous research found in the literature in the form of an S-N curve.